A Clinical Investigation on the Fit of Full Cast Crowns Made by Various Impression Materials and Investment Techniques

Abstract

The indirect method of full cast crown construction has been constantly improved by the introduction of new dental materials and impression techniques. However, the ideal materials and a technique for making crowns with a complete marginal fit have not been developed yet.
The purpose of this study was to clarify the influence of the indirect method on marginal fit of crown by altering various factors.
1. Conventional or fast-setting gypsum-bonded investments.
2. Three different types of impression materials: addition silicone with individual tray, double-mixed addition silicone and agar with irreversible hydrocolloid.
3. Water-saturated or dry ring lining material.
A microscope was used to measure the fit of castings. The fit of castings was defined as the casting margin difference from the original position when they were tried on a steel die.
The fit of castings made in the method using fast-setting gypsum-bonded investment was looser and the marginal difference was significantly smaller than that using conventional gypsum-bonded investment irrespective of the impression material and usage of ring lining materials.